Many articles (e.g., medical instruments and devices) and enclosed regions of a wide range of facilities (e.g., medical treatment and research facilities, pharmaceutical manufacturing facilities, animal research facilities, laboratories, patient rooms, hotel rooms, offices, cruise ships, recreational facilities and vehicles) are treated with a vaporous deactivating agent (e.g., vaporized hydrogen peroxide) in a microbial deactivation process to deactivate microbial contamination on the articles or contaminated surfaces within the enclosed region. In order to determine whether the treated articles or enclosed regions have been successfully deactivated, and thereby safe for use, it is necessary to determine whether all of the parameters necessary for deactivation were met during the deactivation process or are present within the enclosed region during the microbial deactivation process. To this end, biological indicators accompany the articles, or are located within the enclosed region, throughout the microbial deactivation process. A typical biological indicator includes a known number of microorganisms (usually bacterial spores) of known resistance to the mode of deactivation, located in or on a carrier (also referred to as a “coupon” or “strip”), and enclosed in a protective package. Before the microorganisms are deposited onto the carrier, the microorganisms are typically suspended in a suspension medium. Subsequent growth or failure of the microorganisms to grow, i.e., after the deactivation process, under suitable conditions indicates the efficacy of the microbial deactivation process.
Known biological indicators include a carrier formed of a metal, such as stainless steel. The carrier has a uniform flat surface on one side of the carrier, upon which microorganisms are deposited. The carrier is typically enclosed within the protective package having one side formed of a material permeable to a vaporous deactivating agent (e.g., Tyvek®) and having the other side formed of a material impermeable to the vaporous deactivating agent (e.g., Mylar®). The carrier is oriented within the package such that the side of the carrier having the microorganisms thereon faces the permeable side of the package, while the opposite side of the carrier faces the impermeable side of the package.
One problem with known biological indicators is that microorganisms become “stacked” on the surface of the carrier, thereby shielding some of the microorganisms from exposure to the vaporous deactivating agent. FIG. 1 illustrates a prior art biological indicator 70 comprised of a carrier 72 having microorganisms 78 suspended within a suspension medium 76. Suspension medium 76 is deposited onto the flat upper surface of carrier 72. As shown in FIG. 1, microorganisms 78 are “stacked” within suspension medium 76 due to suspension medium 76 failing to more evenly distribute across the upper surface of carrier 72.
Still another problem encountered with known biological indicators is that microorganisms disposed on the flat upper surface of the carrier come into contact with the package enclosing the carrier. As a result, microorganisms can be removed from the carrier. Once removed from the carrier, microorganisms may migrate to the opposite side of the carrier facing the impermeable packaging. As a result, the microorganisms may be “masked” from the deactivation process.
Yet another problem with known biological indicators is that the carrier may shift positions within the protective package, thereby causing the side of the carrier having microorganisms deposited thereon to face the impermeable side of the protective package. Accordingly, exposure of the microorganisms to the vaporous deactivating agent is inhibited.
The problems described above result in a biological indicator that does not accurately indicate the efficacy of a microbial deactivation process.
The present invention overcomes these and other problems by providing an improved biological indicator for determining the efficacy of a microbial deactivation process using a vaporous deactivating agent, and a method for making said biological indicator.